Do you envy those lean people who have a lightning-fast metabolism that lets them eat whatever they want without gaining a pound? You’ve probably known people like that, most of them young. As we age and lose lean body mass, our metabolisms slow, especially if we don’t lift weights.
Though having a fast metabolism might allow you to eat that glazed donut and Frappuccino with whipped cream without gaining an ounce, having a supercharged metabolism isn’t necessarily conducive to long-term health and longevity. In fact, research suggests having a slower one may offer longevity advantages.
What Defines Your Resting Metabolic Rate?
You have a certain resting metabolic rate, the rate at which your body burns energy to sustain bodily functions at rest. These include activities like brain function, maintaining heart contractions and blood circulation, cellular function, breathing, and body temperature regulation.
Your resting metabolic rate is partially determined by genetics, but it also varies based on factors like your age, body weight, how much muscle you carry on your body, how much body surface area you have, and your gender. Men have a resting metabolic rate up to 10% higher than a woman’s, younger people have a faster resting metabolism, and tall, thin people usually have a slightly higher resting metabolic rate because they have more surface area exposed to the outside world.
Your resting metabolism fluctuates to some degree over a 24-hour day, slowing during sleep and increasing when you’re anxious, stressed or have a fever. People who produce too much thyroid hormone, a condition called hyperthyroidism, have a higher resting metabolism and other symptoms of an overactive metabolism like a rapid heart rate, heat intolerance, sweating, and anxiety.
Beyond Resting Metabolic Rate
Your daily energy expenditure is also impacted by two other metabolic components: thermic effect of activity and the thermic effect of eating. Thermic effect of activity is the additional calories you burn when you move around or exercise and usually makes up between 25% and 35% of your daily energy expenditure. Thermic effect of eating is the extra calories you burn to digest, process, and store the food you eat. It usually makes up about 10% of your daily energy expenditure.
So why wouldn’t it be beneficial to have a fast resting metabolism? As Joel Fuhrman M.D., director of functional medicine at Cleveland Clinic points out, preliminary research shows having a slower metabolic rate or rate or energy expenditure could prolong life. In one study, where researchers followed participants for almost 15 years, the participants’ risk of mortality went up with each 100-calorie rise in resting energy expenditure.
Fast Metabolism: More Cellular Wear and Tear
Why would having a faster metabolism be unhealthy? If you buy a car and stress the engine by driving at fast speeds, the engine and the car accumulates wear and tear faster, especially if you don’t maintain it. The same applies to your body. With a higher metabolic rate, cells are subject to more “wear and tear” in the form of free radical damage that ultimately damages cells and shortens their longevity. Having a turbocharged metabolic rate might sound like a gift, but it may also speed up the aging process by increasing damage to cells and tissues and by increasing free radical production.
You may have heard that calorie restriction and periods of fasting prolong life in some animal species. Although this is unproven in humans, when you consume fewer calories, your resting metabolism slows slightly as do other bodily functions, so cells are exposed to less oxidative stress and form fewer free radicals.
At the other end of the spectrum, over-eating raises your metabolic rate and also exposes cells to more cell-damaging stress. In support of this, some studies show people with mildly reduced thyroid function, and thus a slower metabolic rate, have greater longevity.
This doesn’t mean you should drastically cut your calories with the hope of living longer. Doing so could lead to nutritional deficiencies that are even more detrimental. Striking a happy medium from a dietary standpoint is the way to go. Choose nutrient-dense foods that are satisfying and aren’t high in calories and don’t overeat. An occasional 16 hour fast may also be beneficial from a health standpoint.
The Best Way to Boost Your Metabolic Rate is Through Exercise
When you work out, you increase calories the calories you burn because you’re actively moving. As a result, the thermic effect of exercise increases but not your resting metabolic rate. Exercise does produce short-term oxidative stress, but it also activates your body’s internal antioxidant defense system that lies inside muscle tissue and is turned on in response to exercise. Ultimately, the stress of exercise gives cells greater protection against oxidative stress. That’s a good thing!
The short-term increase in free radicals in response to exercise has another benefit – it increases insulin sensitivity. Better insulin sensitivity is linked with a lower risk for heart disease, type 2-diabetes, and, possibly, longevity. Plus, research clearly shows regular physical activity prolongs lifespan. In fact, a National Cancer Institute Study showed regular exercise prolongs life by as much as 4.5 years. Nothing to sneeze at!
The Bottom Line
Don’t lament the fact that you don’t have a naturally fast metabolism. From a health standpoint, a slower metabolic rate could slow the cellular aging process and, potentially, add additional years to your life. Besides, if you had a super fast metabolism, you’d be tempted to stuff your face with too many of the wrong foods because you could get by with it.
The best kind of metabolic boost is the one you get from working out. Not only does exercise burn calories, it also gives you greater protection against cellular “wear and tear” by turning on your internal antioxidant defense system. Exercise burns calories AND it has its own anti-aging benefits. There’s no end to the good things that happen when you work out.
Rozing, M.P., et al.Familial Longevity Is Associated with Decreased Thyroid Function.
J Clin Endocrinol Metab, 2010.
Reuters. “Is lower thyroid activity linked to longevity?”
Dr. Fuhrman. “Slow Metabolism Linked to Longevity”
Is Exercise the Best Antioxidant Supplement? Len Kravitz, Ph.D.
American Journal of Clinical Nutrition, 72(Suppl), 637S-646S. 2000.
National Cancer Institute. “NIH study finds leisure-time physical activity extends life expectancy as much as 4.5 years”
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